/**

 * Definition for a binary tree node.

 * public class TreeNode {

 *     public int val;

 *     public TreeNode left;

 *     public TreeNode right;

 *     public TreeNode(int x) { val = x; }

 * }

 */

public class Solution {

    Stack<TreeNode> S = new Stack<TreeNode>();

        List<List<TreeNode>> list = new List<List<TreeNode>>();

        private void postNode(TreeNode node)

        {

            if (node != null)

            {

                S.Push(node);

                if (node.left != null)

                {

                    postNode(node.left);

                }

                if (node.right != null)

                {

                    postNode(node.right);

                }

                if (node.left == null && node.right == null)

                {

                    list.Add(S.ToList());

                }

                S.Pop();

            }

        }

        public int MinDepth(TreeNode root)

        {

            postNode(root);

            var min = int.MaxValue;

            if (list.Count == )

            {

                min = ;

            }

            foreach (var l in list)

            {

                var count = l.Count;

                if (count < min)

                {

                    min = count;

                }

            }

            return min;

        }

}

 class Solution:

     def minDepth(self, root: TreeNode) -> int:

         if root == None:

             return

         left = self.minDepth(root.left)

         right = self.minDepth(root.right)

         if left ==  or right == :

             return left + right +

         return min(left,right) +